It is commonly known that most conventional surveying instruments have limited applications; for example, a level surveying instrument is only good for level surveying, and a theodolite is only good for surveying angles or inclinations. They not only lack versatility but also lack efficiency because of such essential drawbacks as:
(1) Conventional theodolites or plane boards (that can be used only for surveying angles or levels) are heavy. In surveying operations there is a need for several different types of instruments to be used in combination, which is both inconvenient. Furthermore, these instruments tend to break down easily.
(2) When surveying an angle, the angle can not be measured quickly, and a slow adjustment by hand is required before the angle can be measured.
(3) The manufacture of each type of conventional instrument is complicated and the cost is very high; therefore, it is uneconomical to use conventional instruments.
(4) Theodolite, level surveying instrument and plane boards are hard to use by field engineers in architecture, civil engineering, plant building and irrigation work, thus the application of these three instruments is limited.